Railway signaling



March 8,1921.

' L. O. GRONDAHL RAILWAY SIGNALING Origizia] Filed Dec. 9. 1921 2Sheets-Sheet 1 'INVENTOR'.

ATTORNEY vMamh' $831927" L. o. GRONDAHL RAILWAY S IGNALING OriginalFiled Dec.,9. 1921 2 Sheets Sheet 2 INVENTOR 2 A 4- ATTORNEY PatentedMar. 8, 1927.

UNITED STATES PATENT OFFICE. i

LABS O. GRONDAHL, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO THE UNIONS'WITCI'I 8c SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATIONOF PENNSYLVANIA.

RAILWAY SIGNALING.

Application filed December 9, 1921, Serial No". 521,147. Renewed August2, 1926.

' My invention relates to railway signaling, and is particularly welladapted to signaling of the type wherein roadside signals are governedby track circuits which in turn are controlled by the passage of cars ortrains along the track.

I will describe several forms of signaling apparatus embodying myinvention, and will then point out the novel features there of inclaims.

In the accompanying drawings, Fig. 1 is a diagrammatic View showing oneform of apparatus embodying my invention. Figs. 2 and S are viewsshowing modifications of the apparatus shown in Fig. 1.

Similar reference characters refer to similar parts in each of theseveral views.

Referring first .to Fig. 1, the reference characters F and F designatethe track rails of a railway along which traffic normally moves in thedirection indicated by the arrow. These rails are divided into aplurality of successive track sections A'B, BC, C-D, etc., the isolationof the track sections being accomplished, as here shown, by insulatedjoints 2 in both of the lines of rails. Any other suitable method ofisolating the sections may be employed, however, without departing fromthe spirit and scope of my invention.

Located adjacent the entrance end of each track section is a signaldesignated by the reference character S, with an exponent correspondingto the location. Each signal, as here shown, comprises three lamps G, Yand R, which, when lighted, indicate proceed, caution and stop,respectively.

Each track section is provided with a track circuit comprising a sourceof current and a relay. As here shown, the source of current for eachtrack circuit is the secondary 3 of a transformer designated by thereference character T with an exponent corresponding to the location,the primary 22 of which is connected with a transmission line 5 to whichalternating current is constantly supplied by a generator l. The relayfor each track circuit is designated K, and is of the thermo-sensitivetype comprising a heating element 6 and thermo-sensitive ele ment 7 theheating element being connected across the rails adjacent the entranceend of the section. The thermo-sensitive relay K has a negativetemperature coefficient, that is, the resistance of the element 7decreases With increase of temperature, and so with increase of currentflowing in the heating element 6.

Referring specifically to signal S the proceed lamp G is provided with acircuit which passes from the left-hand terminal of secondary 8 oftransformer T through a ballast resistance 9, wire 10, heating elementof a thermo-sensitive relay K wire 11, lamp G, wire 12,thermo-sensit-ive element of the relay K, and wire 13 to the right-handterminal of secondary 8. Connected across the secondary 8 and in shuntwith the other elements of the circuit just traced are the heatingelements of two thermo-sensitive relays K and K Each relay K K and K hasa negative temperature coefficient. The parts of this circuit are soadjusted that when relay K is energized, that is, when track section A-Bis unoccupied, sufiicient current flows through lamp Gr to light thislamp and the current in the heating element of relay K is stiflicient toenergize this relay. The drop in voltage across the several elements inthe circuit is then such that relays K and K are tie-energized. hensection AB is occupied by a car or train, however, relay K isole-energized and the current which then flows through lamp G isinsufficient to light this lamp. The voltage drop across lamp G andrelays K and K is then such that relays K and K become energized.

The stop lamp R for signal S is provided with a circuit which includes asecondary 14 of transformer T and the thermosensitive element of relay KThe parts of this circuit are so adjusted that when relay K isole-energized, lamp R is extinguished, but that when relay K becomesenergized, such as when section A-B is 0ccupied by a car or train, theamount of current which flows in the circuit is sufiicient to light thestop lamp R.

The caution lamp Y for signal S is pro vided with a circuit which passesfrom the left-hand terminal of secondary 15 of transformer T throughwire 16, thermo-sensitive element of relay K at location A, wires 13, 17and 11, thermo sensitive element of relay K primary of transformer 19,wire 20, lamp Y, and wire 21 to secondary 15 cf transformer T The partsof this circuit are so adjusted that when relays K and K are bothenergized, the current which flows in lamp Y is sufficientto light thislamp, but that when either of the said relays becomes de-energized, thecurrent is reduced to such value that lamp Y is extinguished.

The secondary of transformer 19 is connected with the heating element ofa thermosensitive relay K having a negative temperature coeflicient andthe thermo-sensitive element of which is connected across the terminalsof the proceed lamp G.- The purpose of this transformer and relay is tosuppress or extinguish lamp G when the caution lamp Y of the same signalis burning. To do this, the parts are so adjusted that when lightingcurrent is supplied to lamp Y, the secondary of transformer 19 deliverssufficient current to energize relay K, so that a shunt of lowresistance is provided around lamp G. Then lamp Y is extinguished,however, the current in transformer 19 is not of sufficient value toenergize relay K and so the shunt around lamp G has a comparatively highresistance, and this shunt does not then divertsufticient current fromlamp G to extinguish this lamp.

As shown in the drawing, the track section to the left of location A isoccupied by a car or train W, so that relay K at location A isde-energized. Lamp G of signal S is accordingly extinguished and thesame thing is. true of lamp Y, because of. the fact that relay Y atlocation A is tie-energized. Relay K at location A is energized,however, so that stop lamp R is lighted. At location B the stop lamp Ris extinguished because the associated relay K is de-energized. Thecaution lamp Y is lighted, however, because relay K at signal S andrelay K at signal S are both energized. The proceed; lamp G of signal Sis extinguished because the adjacent relay K is energized. At signal Sthe stop lamp R is extinguished because the adjacent relay K isdeenergized, and the caution lamp Y is extinguished because relay K5 atlocation B is de-energized. The proceed lamp G is lighted, however,because the adjacent track relay K is energized.

Referring now to Fig. 2, the track circuits are the same as in Fig. 1,,but the control of. the signals by these track circuits is somewhatdiflerent. Considering location B, for example, the track relay Kcontrols a circuit which passes from the lefthand terminal of secondary8 of transformer T through resistance 9, heating element of a relay Ithermo-sensitive element of relay K, heating element of a relay K andwires 22 and 23 to the secondary 8 of transformer T The stop lamp R isconnected in this circuit in shunt around relays K, K and K so that thislamp is connected with secondary 8, but with a resistance 9 interposedbetween the secondary and the lamp. The parts of the circuit are soadjusted that when relay K is energized, relays K and K are alsoenergized and the voltage across lamp R is insufficient to light thislamp; but that when relay K is tie-energized, due, for example, to thepresence of a car or train in section A-B, relays K and K also becometie-energized and the voltage which is then applied to lamp R issufficient to illuminate this lamp.

The proceed lamp G of signal S is provided with a circuit which passesfrom the left-hand terminal of secondary 24 of transformed T throughresistance 29, wire 32, thermo-sensitive element of relay K at locationA, wire 81, lamp G, wire 30, thermosensitive element of relay K atlocation B, and wires 26 and 25 to secondary 24 of transformer T. Theparts of this circuit are so adjusted that lamp G is lighted only whenrelay K at location A and relay K at location B, are both energized.

The caution lamp Y at location B is provided with a circuit which passesfrom secondary 24 of transformer T through resistance 29, wire 28, lampY, wire 27, thermosensitive element of relay K and wires 26 and 25 tosecondary 2a: of transformer T. The parts of this circuit are soadjusted that lamp Y is lighted when the adjacent relay K is energizedprovided that lamp G of the same signal is extinguished. To accom plishthis operation of lamps G and Y, lamp G is preferably a low voltagelamp, such as 6 volts, while lamp Y is a high voltage lamp, such as 110volts. The resistance 29 being in series with both lamps, it is thenobvious that lamp G and thermo-sensitive relay K constitute a shunt oflow resistance around lamp Y, so that when lamp G is illuminated lamp Ywill be extinguished.

As shownv in the drawing, the track section to the left of location A isoccupied by a car or train so that traclr relay K at location A isde-energized. It follows that lamp R of signal S is lighted because ofthe high resistance of the thermo sensitive element of relay K, and sosignal S inclicates stop. As for signal S, the stop lamp R isextinguished because the adjacent relay K is energized, and the proceedlamp G is extinguished because relay K at location A is de-energized.The caution lamp Y is lighted, however, because the adjacent relay K? isenergized. In signal S the stop lamp R is extinguished because theadjacent relay K is energized, and the proceed lamp G is Hill Cir

lighted because the adjacent relay K and the relay K at location B areboth energized. The caution lamp Y is extinguished because this lamp isshunted by lamp G of the same signal and relay K at location B.

Referring now to Fig. 3, the track circuit is again the same as in Fig.1, but the control of the signal lamps by the track relays isaccomplished with a still different arrangement of circuits andapparatus. In this View each track relay K controls a circuit whichincludes thesecondary 8 of the adjacent transforn'ier T, as well as theheating elements of four thermo-sensitive relays K K K and K all ofwhich relays will consequently be energized when the corresponding tracksection is unoccupied and de-energized when the track section isoccupied.

The stop lamp R of each signal is connected directly across secondary 14of the adjacent transformer T, but this lamp is provided with a shunt orbranch circuit which includes the thermo-sensitive element of theadjacent relay K". The iarts of this circuit are so adjusted that lamp Rwill be extinguished when relay K is energized, and lighted when relay Kis de-energized; that is, when relay K is energized the resistance ofthe thermo-sensitive element of this relay so low that sufficientcurrent is diverted from lamp R to extinguish the lamp, or to expressthe matter in another way, the volt age across this lamp is theninsutlicient to light the lamp.

The proceed lamp G of signal S is provided with a circuit which passesfrom secondary 32 of transformer T through wires 34: and 34, lamp Gr,wire 35, thermo sensitive element of relay K at location B, wires 36 and37, thermo-sensitive element of relay K at location A, and wire 38 tosecondary 33 of transformer TA. The parts of this circuit are soadjusted that lamp G is lighted when both relays K and K are energized,but extinguished when'either of these relays is de-energized.

The caution lamp Y of signal S is included in a circuit which passesfrom secondary 15 of transformer T thou h Wire 41*, lamp Y, wire 41,primary or transformer 42, wire 40, heating element of relay K, wire 35,thermo-sensitive element of relay K and wire 39 to secondary 15. Thiscircuit is so adjusted that lamp Y is lighted when relay K is energized,provided that the secondary of transformer 42 is not supplied withcurrent by induction from the primary of this transformer which primaryis connected directly across wires 34 and 37 in the circuit for theproceed lamp G.

iVhen transformer 42 at location B is energized by current fromsecondary 33 at loca tion A, however, the current flowing in lamp Y fromthe adjacent secondary 15 is suppressed so that lamp Y is extinguished.On the other hand, when lamp Y is lighted, the adjacent relay'K isenergized and the thermo-sensitive element of this relay then forms alow resistance shunt around the adjacent lamp Or so that this lampisextinguished.

As shown in the drawing, the section to the left of location A isoccupied by a car or train W, so that track relay K at location A istie-energized with the result that relays K, K K and K at this locationare also tie-energized. Owing to the fact that relay K is de-energized,the stop lamp R of signal S is lighted, so that this signal indicatesstop. Considering signal S the proceed lamp G is extinguished becauserelay K at location A is de-energized. The cantion lamp Y is lightedbecause relay K at location B is energized and the primary oftransformer 42 is tie-energized, due to the fact that relay K atlocation A is de-energized. The stop lamp R is extinguished because theadjacent relay K is energized. At signal S the proceed lamp G is lightedbecause relay K at this signal and relay 1 at location B are bothenergized. The cantion lamp Y is extinguished because the currentsupplied to this lamp by the adjacent secondary 15is neutralized bycurrent supplied to the adjacent transformer 42 from secondary oftransformer T. The stop lamp R is extinguished because the adjacentrelay K is energized.

I have found that of the thermo-sensitive materials suitable for use inthermo-se-nsitive relays, those having negative temperature coefficientsare more numerous and more conveniently handled than those havingpositive temperature coefiicients. Furthermore, it is known that thecoefficients of the nega tive temperature coefficient substances areenormously greater in general than the coefficients of the positivetemperature coefficient substances that may be readily utilized. Itfollows, therefore, that for relays of this character substances havingnegative temperature coetficients are preferable to substances havingpositive temperature coefficients. One feature of the present inventionis that all of the t-hermo-sensitive relays have negative temperatureooefhcients.

Although I have herein shown and described only three forms of signalingapparatus embodying my invention, it is understood that various changesand modifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a plurality of successive sections of railway track,a track circuit for each section including a source of current and theheating element of a thermosensitive relay K; a signal "for each sectioncomprising proceed, caution and stop lamps; a circuit for the proceedlamp of each signal including a source of current, the thermosensitiveelement of relay K and the heating element of a thermo-sensitive relay,K a branch for each proceed circuit passing around said lamp,thermo-sensitive element, and heating element, and including the heatingelements of two thermo-sensitive relays K and 1G; a circuit for the stoplamp of each signal including a source of current and thethermo-sensitive element of relay K a circuit for the caution lamp ofeach signal including a source of current, the thermosensitive elementof the adjacent relay K the thermo-sensitive element of relay K at thenext signal in advance and the primary of a transformer; athermo-sensitive relay K for each signal the heating element of which isconnected with the adjacent transformer, and a shunt around each proceedlamp including the thermo-sensitive element of the adjacent relay 1 2.1n combination, a plurality of successsive sections of railway track, atrack circuit for each section including a source of current and theheating element of a thermo-sensitive relay K; a signal tor each sectioncomprising proceed, eaution and stop lamps; a circuit tor the proceedlamp of each signal including a source of current, the thermo-sensitiveelement ofv relay K and the heating element oi a thermosensitive relay Ha branch for each proceed circuit passing around said lamp,therino-sensitive element and heating element and including the heatingelements or two thermo-sensitive relays K and K; a circuit for the stoplamp of each signal including a source of current and the thermo-sensitive element of relay K"; a circuit for the caution lamp of eachsignal including a source of current, the thermo sensitive element ofthe adjacent relay K and the therinc-sensitive element of relay K at thenext signal in advance; and means for each signal controlled by the flowof current in the caution lamp for preventing the supply of current tothe proceed lamp.

3. In combination, a stretch of railway track comprising a plurality ofsuccessive sections, signals for said sections, and traincontrolledmeans for governing said signals comprising thermo-sensitive relays eachmade up of a heater and a thermosensitive elementand all suchthermo-sensitive elements having n'agative temperature cociiicients.

4;. In combination, a stretch oi? railway track comprising a pluralityof successive sections, signals for saidsections each adapted toindicate proceed, caution and stop, and train-controlled means forgoverning said sections comprising thermo-sensitive relays each made upof a heater and a thermo-sensitive element and all such thermosensitiveelements having negative temperature coei'licients.

5. In combination, a stretch of railway track comprising a plurality ofsuccessive sections, signals for said sections each adapted to give atleast two indications, traincontrolled means for governing said signals,and means for each signal including a therinc-sensitive relay controlledby the current which causes the signal to give one indication forpreventing the signal from simultaneously giving a different indication.

(3. In combination, a stretch of railway track comprising a plurality ofsuccessive sections, signals for said sections each having at least twodevices adapted when supplied with current to give contradictoryindications, and means for each signal including a therino-sensitiverelay controlled by the current supplied to one device for preventingthe sin'iultaueous supply of current to another device in the samesignal.

7. In combination, two successive sections of railway track, a tackcircuit for each section including a source of current and the heatingelement of a thermo-sensitive relay having a negative temperaturecoeflicient, a signal for the rear section including a device adaptedwhen energized to cause the signal to indicate proceed, and meanscontrolled by the thermo-seusitive elements of said thermo-sensitiverelays and eiiective only when both of said sections are unoccupied forcausing said device to be energized.

8. In combination, two successive sections of railway track, a trackcircuit for each section including a source of current and the heatingelement of a thermo-sensitive relay having a negative temperaturecoe'liicient. a signal for the rear section including a lamp adaptedwhen energized to indicate proceed, and means controlled by thetl1ermosensitive elements of said thermo-sensitive relays and effectiveonly when both of said sections are unoccupied for causing said lamp tobe encrgized.

9. In combination, two successive sections of railway track, athermo-sensitive relay for each section, train controlled means for aidsections for causing the relay for the rear section to be conductiveonly when its section is unoccupied and the relay for the forwardsection to be conductive only when its section is occupied, and a sign lfor the rear section controlled by said relays and adapted to indicatecaution when both of said relays are conductive.

10. In combination, two successive sections 01 railway track, athermo-sensitive relay for each section, train controlled means for saidsections for energizing one relay when its section is unoccupied and theother relay when its section is occupied, and a signal controlled bysaid relays and adapted to indicate caution when both relays areenergized.

11. In combination, two successive sections of railway track, athermo-sensitive relay for each section, train controlled means for saidsections for energizing the relay for the rear section when its sectionis unoccupied and the relay for the forward section when its section isoccupied, and a signal controlled by said relays and indicating cautionwhen both relays are energized.

In testimony whereof I affix my signature.

LABS O. GRONDAHL.

